The use of solid-state modules is widespread in the fields of electronic and photonic communication, television and radio, radar, and other surveillance and signal processing contexts. In some contexts, notably surveillance and signal processing, it is important to maximize the performance of the various solid-state devices.
Solid-state devices are made in a variety of ways. Photolithography is often used to mask one or more portions of the surface of a semiconductor wafer. Dopant materials are introduced into the atmosphere surrounding the wafer, and the temperatures are adjusted to cause the dopants to diffuse into the surface of the wafer, to thereby affect the conductivity in portions of the wafer. This process is repeated with various dopant materials and other materials, so as to generate many devices on the surface of the semiconductor wafer. When complete, the wafer is broken or sawed into sections having the desired number of semiconductor devices in each section. In this manner, devices including hundreds, thousands, or tens of thousands of active devices can be fabricated in a structure less than a centimeter on a side. The ability to fabricate hundreds or thousands of such devices by processing a single semiconductor wafer allows very low unit cost, which has driven the microelectronics boom.
It is well known that transistors are adversely affected by high temperatures. In this context, thermally induced dopant migration in the solid-state wafer material is a major contributor to failure of solid-state devices. It is important, therefore, to maintain the temperatures of solid-state devices below some value, which is deemed to provide the desired operational lifetime. Thus, it may be desirable to keep a silicon solid-state device at a temperature of less than 150° Celsius (C.), even though it may operate (albeit for a shorter period of time) at 200° C. Generally, similar temperature criteria apply to Gallium Arsenide MMIC devices used in radar applications.
The operating frequencies of solid-state devices for the above mentioned applications keep rising, as more functionality is demanded. As for example, the operating clock frequencies of computers continue to increase in order to provide faster processing. Also, the power handled by solid-state devices tends to increase, as improved performance is required. For example, Monolithic Microwave Integrated Circuit (MMIC) devices for use in array antennas for radar surveillance are required to produce ever-increasing amounts of transmitter power. High power and high operating frequency are closely related to temperature in a solid-state device. In many cases, achieving the desired power level requires the combining or arraying of a plurality of solid-state devices or modules. The close spacing of solid-state devices in these contexts, in turn, tends to increase the power density within the combination or array, which exacerbates the problem of maintaing temperature. The cooling of solid-state devices has become a major consideration in the design of electronic and photonic systems.
The prior art includes various patents describing various approaches to the cooling of modules. Such an arrangement is described in U.S. Pat. No. 5,459,474, issued Oct. 17, 1995 in the name of Mattioli et al. The Mattioli et al. arrangement includes an array of horn-like elemental antennas fabricated in a conductive plate, with little room to the rear of the antennas for electronic devices. The Mattioli et al. arrangement includes a slide-in carrier bearing the electronic modules, which carrier mates with the elemental antennas. In the Mattioli et al arrangement, the modules are mounted on carriers, which are fastened to cold plates cooled by circulation of coolant liquid. U.S. Pat. No. 6,465,730, issued Oct. 15, 2002 in the name of Pluymers et al. describes a method for mating electronic modules in a high-density context, to provide heat transfer to a cold plate.
Attention has been directed in the prior art toward moving the cold plate closer to the actual source of the heat. U.S. Pat. No. 6,388,317, issued May 14, 2002 in the name of Reese, describes a module in which the solid-state device to be cooled is mounted on a thermally conductive carrier, and the carrier contains microchannels through which coolant liquid is circulated.
Improved or alternative cooling arrangements are desired for solid-state devices.